ch. 9 shoulder girdle
if the humerus does up 30 degrees, how much has the scapula moved?
0 degrees
In the resting position, the scapula is located between what ribs?
2nd and 7th
The articulation of the lateral end of the clavicle and superior scapula
Acromioclavicular joint
term commonly used to describe the various amounts of ligament injury at the AC joint. In a first-degree sprain, the acromioclavicular ligament
Acromioclavicular separation In a first-degree sprain, the acromioclavicular ligament (see Fig. 9-8) is stretched. In a second-degree sprain, the acromioclavicular ligament is ruptured, and the coracoclavicular ligament (see Fig. 9-8) is stretched. In a third-degree sprain, both the acromioclavicular and coracoclavicular ligaments are ruptured.
understanding synonymous terms
At this joint, protraction and abduction are synonymous terms, as are retraction and adduction. For example, shoulder girdle protraction and retraction is synonymous with scapular abduction and adduction. Scapular rotation is the same as shoulder girdle rotation.
serratus anterior muscle prime mover
Because it has a nearly horizontal line of pull outward, it is a prime mover in scapular protraction.
upper trapezius muscle line of pull and action
Because its line of pull is more vertical (upward) than horizontal (inward), it is a prime mover in scapular elevation and upward rotation and is only an assisting mover in scapular retraction.
account for the most frequently broken bone in children. They usually result from a fall on the lateral aspect of the shoulder or on the outstretched hand. The clavicle usually breaks in its midportion.
Clavicular fractures
Innervation of Trapezius
Cranial nerve XI (accessory nerve) C3, C4 (sensory)
Levator scapula innervation
Dorsal scapular C3, C4, C5
Rhomboids innervation
Dorsal scapular C5
When two or more muscles pull in different directions to create a combined action
Force couple
The shoulder joint consisting of the articular surfaces of the humeral head and glenoid fossa of the scapula
Glenohumeral joint
A ring of fibrocartilage that lines the lip of the glenoid cavity
Glenoid labrum
The compression of structures caused by narrowing of the space surrounding them or encroachment of tissue into the space
Impingement
Identify the muscles that form the force couples responsible for upward rotation of the scapula of the shoulder girdle.
In the case of the shoulder girdle, the upper trapezius muscle pulls up, the lower trapezius muscle pulls down, and the lower fibers of the serratus anterior muscle pull outward in a horizontal direction. The net effect is that the scapula rotates upward
type of joint and motion of AC joint
It is a plane-shaped synovial joint that allows a gliding motion to occur, contributing toward movement in three planes of motion
lower trapezius muscle line of pull and action
Its diagonal line of pull is more downward (vertical) than inward (horizontal), making it a prime mover in depression and upward rotation of the scapula and only an assisting mover in retraction.
middle trapezius muscle
Its line of pull is horizontal, which makes it very effective at scapular retraction. Because the line of pull passes just above the axis for upward rotation, its role in scapular upward rotation is only assistive.
Serratus anterior innervation
Long thoracic C5, C6, C7
Pectoralis minor innervation
Medial pectoral C8, T1
Occurs when the distal segment is fixed or stable and the muscle pulls the origin toward insertion
Reverse muscle action
The tendinous insertions of the subscapularis, infraspinatus, teres minor and supraspinatus muscles on the tubercles of the humerus
Rotator cuff
Elevation of the arm in the plane of the scapula
Scaption
Approximately 30 degrees forward of the frontal plane
Scapular plane
occurs when the scapula moves away from the posterior midline
Scapular protraction (scapular abduction)
Movement of the inferior angle of the scapula posteriorly
Scapular tilt
occurs when the shoulder joint goes into hyperextension.
Scapular tilt The superior end of the scapula tilts anteriorly, and the inferior end tilts posteriorly. Examples of these combined motions are the "windup" or prerelease phase of a softball pitch, a bowling delivery, or a racing dive in swimming.
the posterior lateral movement of the vertebral border of the scapula in the transverse plane. In other words, the vertebral border of the scapula moves away from the rib cage.
Scapular winging Winging of the scapula (posterior view). This person's right serratus anterior muscle is paralyzed. When pushing against the wall with both hands, the right scapula rises away from the rib cage, standing out like a small wing.
A term used to describe the ratio of normal motion between the glenohumeral and scapulothoracic joints
Scapulohumeral rhythm
a concept that further describes the movement relationship between the shoulder girdle and the shoulder joint.
Scapulohumeral rhythm The first 30 degrees of shoulder joint motion is pure shoulder joint motion. However, after that, for every 2 degrees of shoulder flexion or abduction that occurs, the scapula must upwardly rotate 1 degree. This 2:1 ratio is known as scapulohumeral rhythm. after the first 30 degrees, the scapula will need to lift/move in order to allow the full range of motion. for every 2 degrees the arm goes up at the glenohumeral joint, there is one degree at the scapulothoracic joint
The articulation of the anterior surface of the scapula against the posterior ribs
Scapulothoracic joint
A ring of bony articulations consisting of the acromioclavicular joints, sternoclavicular joints, and scapulothoracic joints
Shoulder girdle
term often used to discuss the activities of the scapula and clavicle and, to a lesser degree, the sternum and ribs.
Shoulder girdle
The articulation of the medial end of the clavicle and lateral sternum
Sternoclavicular joint
Identify the muscles that form the force couples responsible for downward rotation of the scapula of the shoulder girdle.
The combined effects of the pectoralis minor muscle pulling down, the rhomboid muscles pulling in, and the levator scapula muscle pulling up is downward rotation of the scapula
The shoulder girdle and glenohumeral joints combined
The shoulder complex
this joint consists of the scapula and humerus. what is it called and what are the motions?
The shoulder joint, also called the glenohumeral joint, consists of the scapula and humerus. The motions of the shoulder joint are flexion, extension and hyperextension, abduction and adduction, medial and lateral rotation, and horizontal abduction and adduction.
five muscles primarily responsible for moving the scapula
Trapezius Levator scapula Rhomboids Serratus anterior Pectoralis minor
Movement of the vertebral border of the scapula posteriorly
Winging
Reverse muscle action during crutch walking with hands bearing weight on crutch handles to prevent scapula and rib cage from depressing. The pectoralis minor (A) is pulling up on the rib cage while the lower trapezius (B) pulls up on the vertebral column and pelvis to elevate the body, allowing it to swing through the crutches.
With the shoulder girdle stabilized, the lower trapezius and pectoralis minor can reverse their actions and assist in elevating the trunk. This is particularly useful during crutch walking. With the crutches planted on the floor and the hands bearing weight on the crutches, the scapula becomes stabilized, preventing the lower trapezius and pectoralis minor from depressing the scapula when they contract. Instead, their origins move the body upward toward the scapula, thus raising the body as it swings through the crutches
connects the acromion process of the scapula and the lateral (acromial) end of the clavicle.
acromioclavicular (AC) joint
serves as a shock absorber in the SC joint
articular disk
where does motion occur during elevation and depression of the SC joint
between the clavicle and disk
What does the musculocutaneous nerve innervate?
biceps, brachialis
what makes up the shoulder girdle
clavicle and scapula
Movement of the vertebral border of the scapula medially and inferiorly
downward rotation
combined motions for retraction
downward rotation, depression, adduction
motions of the SC joint
elevation and depression in the frontal plane as well as protraction and retraction in the transverse plane, and rotation occurs along the longitudinal axis of the bone (the clavicle spins on the sternum). Basically, the clavicle moves while the sternum remains stationary.
motions of the shoulder girdle
elevation and depression, protraction and retraction, and upward and downward rotation
The sternoclavicular and acromioclavicular joints allow shoulder girdle motions, including
elevation and depression, protraction and retraction, and upward and downward rotation.
True motions of scapula
elevation, depression, adduction, abduction
shoulder girdle innervation
fairly high off the spinal cord from a variety of sources proximal to the terminal nerves of the brachial plexus.
defined as muscles pulling in different directions to accomplish the same motion
force couple
what part of the trapezus is only the prime mover?
middle
where does motion occur during protraction and retraction on SC joint
motion occurs between the disk and the sternum.
levator scapula muscle prime mover for
named for its function of scapular elevation
rhomboids prime mover
prime mover in retraction and elevation rhomboids rotate the scapula downward.
All three parts of the trapezius muscle work together (synergists) to
retract the scapula.
The actions of the shoulder girdle muscles have been described as moving the insertion toward the origin. However, if the insertion is stabilized, the origin will move. This is called what?
reverse muscle action It allows some of the shoulder girdle muscles to have assistive roles in other joints, primarily the head and neck.
what makes up the shoulder joint
scapula and humerus
what makes up the shoulder complex
scapula, clavicle, sternum, humerus, rib cage, and includes the sternoclavicular joint, acromioclavicular joint, glenohumeral joint, and scapulothoracic articulation. in other words- it includes the shoulder girdle (scapula and clavicle) and the shoulder joint (scapula and humerus)
occurs when the scapula moves inferiorly
scapular depression
the return to the resting anatomical position from the upwardly rotated position.
scapular downward rotation
occurs when the scapula moves in a superior direction
scapular elevation
occurs when the scapula moves back toward the posterior midline.
scapular retraction (scapular adduction)
the inferior angle of the scapula rotates up and away from the vertebral column
scapular upward rotation
not a joint in the pure sense of the word as there is no direct union between the bones, and there is no joint capsule. It consists of the slightly concave anterior surface of the scapula resting on the convex posterior aspect of the rib cage. provides motion necessary for normal function of the scapula.
scapulothoracic articulation
formed by the articulation between the manubrium of the sternum and the medial (sternal) end of the clavicle.
sternoclavicular (SC) joint
The three major ligaments supporting SC joint
sternoclavicular, costoclavicular, and interclavicular ligaments
Rotator Cuff Muscles (SITS)
supraspinatus, infraspinatus, teres minor, subscapularis
convex/concave rule on SC joint during shoulder girdle elevation and depression & During protraction and retraction
the convex surface of the clavicle slides inferiorly and superiorly on the concave manubrium as the clavicle's lateral end moves up and down, respectively. This motion occurs between the clavicle and the disk. the concave portion of the clavicle slides anteriorly and posteriorly on the convex costal cartilage, respectively as the clavicle's lateral end moves forward and backward. This motion occurs between the disk and the sternum.
Scapular motion during upward rotation.
the inferior angle of the scapula rotates up and away from the vertebral column
large, superficial muscle that appears diamond-shaped when looking at both right and left sides. Anatomically it is one muscle, but functionally, it is usually divided into three parts: upper, middle, and lower. The reason for this separation is that there are three different lines of pull (upward, inward, downward) resulting in different muscle actions.
trapezius muscle
prime motions of AC joint
upward and downward rotation in the plane of the scapula The AC joint can also contribute toward scapular tilt in the sagittal plane, and when present, scapular winging in the transverse plane.
Movement of the vertebral border of the scapula laterally and superiorly
upward rotation
combined motions for protraction
upward rotation, elevation, abduction
